feat(acl,domain): cancel the ZGW zaak on document-timeout expiry (S-10c, closes #106) (#109)

## S-10c · Close the ZGW zaak on document-timeout expiry (closes #106)

Completes the S-10a/S-10b boundary flagged in ADR-0017: when a registration's 30-day document term lapses, the domain now cancels the **ZGW zaak** as well as marking the aggregate `Verlopen`, so OpenZaak and the register no longer diverge.

### What it does
On expiry the `ExpireRegistrationWorker` calls the ACL to set the zaak to a distinct, non-terminal **`Geannuleerd`** status with a **`Vervallen`** resultaat (vs the approval `Afgehandeld` + `Geregistreerd`), resolved **by omschrijving** in the ACL — the ACL-first ordering mirrors approval so a failed ZGW call leaves the job for redelivery rather than diverging the two.

**Path:** Flowable P30D timer → `RegistratieVerlopen` job → domain `ExpireRegistrationWorker` → ACL `POST /annuleringen` → ZGW `resultaten` + `statussen` (Geannuleerd) → aggregate `Verlopen`.

### Layers touched (each red→green)
- **ACL gateway** — `SetZaakToCancellationStatusAsync` (Geannuleerd + Vervallen by name); approval now resolves its `Geregistreerd` resultaat by name too (a second resultaattype now exists).
- **ACL service/API** — `AclService.CancelZaakAsync` + `POST /annuleringen`.
- **Domain** — `IAclClient.CancelZaakAsync` + client; expiry worker cancels the zaak before advancing to `Verlopen`, guarded against redelivery double-cancel.
- **Seed** — non-terminal `Geannuleerd` statustype (volgnummer 2; `Afgehandeld` → 3) + `Vervallen` resultaattype, both idempotent by omschrijving and sharing the zaaktype's procestype.
- **Verify/integration** — ACL↔OpenZaak integration test (live `Geannuleerd` + resultaat); `run-domain-check.sh` fires the real P30D timer and asserts the zaak reaches `Geannuleerd` end-to-end; BDD scenario asserts cancel-on-timeout vs untouched-when-in-time.
- **Docs** — ADR-0019 (cancellation modelling decision), demo-script, BACKLOG.

### Design note (ADR-0019)
ZGW allows only one eindstatus per zaaktype, so `Geannuleerd` is modelled as a **non-terminal** status (it records a cancellation status + resultaat but does not set `einddatum`). This follows the issue's explicit "distinct statustype + resultaat" outcome; the shared-eindstatus alternative is recorded in the ADR.

### Tests
Unit + acceptance all green locally (Acl 38, Big 134, Acceptance 17, Bff 33, EventSubscriber 19). Integration + verify-stack run in CI (need live OpenZaak + selectielijst egress).

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Reviewed-on: #109

services/acl/Acl.Tests/AclServiceTests.cs

@@ -23,6 +23,14 @@ public class AclServiceTests
             return Task.CompletedTask;
         }
 
+        public (Uri Zaak, Uri Zaaktype, DateOnly Datum)? Cancelled;
+
+        public Task SetZaakToCancellationStatusAsync(Uri zaakUrl, Uri zaaktypeUrl, DateOnly datumStatusGezet, CancellationToken ct = default)
+        {
+            Cancelled = (zaakUrl, zaaktypeUrl, datumStatusGezet);
+            return Task.CompletedTask;
+        }
+
         public Uri? ReadReferenceFor;
 
         public Task<string> GetZaakIdentificatieAsync(Uri zaakUrl, CancellationToken ct = default)
@@ -126,6 +134,34 @@ public class AclServiceTests
         Assert.Null(gateway.Approved);
     }
 
+    [Fact]
+    public async Task Cancelling_a_zaak_sets_it_to_the_cancellation_status_dated_today()
+    {
+        var gateway = new FakeGateway();
+        var defaults = Defaults();
+        var service = new AclService(gateway, defaults, new FixedClock(new DateOnly(2026, 6, 4)));
+        var zaak = new Uri("http://openzaak/zaken/api/v1/zaken/abc");
+
+        await service.CancelZaakAsync(zaak);
+
+        Assert.NotNull(gateway.Cancelled);
+        Assert.Equal(zaak, gateway.Cancelled!.Value.Zaak);
+        Assert.Equal(defaults.ZaaktypeUrl, gateway.Cancelled.Value.Zaaktype);
+        Assert.Equal(new DateOnly(2026, 6, 4), gateway.Cancelled.Value.Datum);
+        // Cancellation must not touch the approval path.
+        Assert.Null(gateway.Approved);
+    }
+
+    [Fact]
+    public async Task Cancelling_a_null_zaak_is_rejected_without_touching_the_gateway()
+    {
+        var gateway = new FakeGateway();
+        var service = new AclService(gateway, Defaults(), new FixedClock(new DateOnly(2026, 6, 4)));
+
+        await Assert.ThrowsAsync<ArgumentNullException>(() => service.CancelZaakAsync(null!));
+        Assert.Null(gateway.Cancelled);
+    }
+
     [Fact]
     public async Task Storing_a_diploma_default_fills_the_document_fields_and_returns_its_url()
     {